SQL Server string to varbinary conversion

Question

Ok, the problem is that there's a merger or join that needs to be done on 2 tables. One has file content stored as an [image] type or varbinary(max), the other has the file content stored as a hex string. if I upload the same content into both tables

the content as string (bytearray to string) would look like like this...

'application/vnd.xfdl;content-encoding="base64-gzip"
H4sIAAAAAAAAC+y9e1fjONI4/H9/Cg173idwFgIJl+5m6MzPJAayE+KsnXQPs8+cHJMY8HZi57ET
aObMh3918UW2Jcdyrmbg7E7HtqpUpSqVSqWSdPHLj/EIPBuOa9rWl51K+WgHGNbAHprW45edpqYc
fPp0+vmgsvNL7cPFb1eNFoDlLffLztN0Ojk/PHx5eSl3Zo4hDx+N8sAeH6Iyh2fl0x1S8Hwwc6f2'    
...

the content as image looks like (and this is ultimately what I want it to look like)

0x6170706C69636174696F6E

if I do select convert(varbinary(MAX), @contentAsString) I get 0x6100700070006C00690063006100740069006F006E

it appears as though the conversion is on target but putting two zeros (00) between each, I'll call it a byte for lack of better words.

I've tried all sorts of more complicated methods posted across forums but to no avail. Any help would be appreciated.

Answer 1

Ok, so the padded 00 has been answered.

DECLARE @hexStringNVar nvarchar(max)
DECLARE @hexStringVAR varchar(max)

SET @hexStringNVar = '{my hex string as described above}'
SET @hexStringVAR = '{my hex string as described above}'

select CONVERT(varbinary(MAX), @hexStringNVar)) = 0x6100700070006C00690063...
select CONVERT(varbinary(MAX), @hexStringVAR)) = 0x6170706C6963...

The 00 padding is because of Unicode or NVARCHAR as opposed to VARCHAR.

So, since the stored data is in nvarchar(max), the solution is this:

select CAST(cast(@hexStringNVar as varchar(max)) as varbinary(max)) = 0x6170706C6963...

I'm sure that convert would work just as well but my target SQL Server is 2005.

Answer 2

From MSDN

In SQL Server 2008, these conversions are even more easier since we added support directly in the CONVERT built-in function. The code samples below show how to perform the conversion(s):

declare @hexstring varchar(max);

set @hexstring = '0xabcedf012439';

select CONVERT(varbinary(max), @hexstring, 1);

set @hexstring = 'abcedf012439';

select CONVERT(varbinary(max), @hexstring, 2);

go

declare @hexbin varbinary(max);

set @hexbin = 0xabcedf012439;

select
   CONVERT(varchar(max), @hexbin, 1),
   CONVERT(varchar(max), @hexbin, 2);

go